U.S. patent application number 12/047064 was filed with the patent office on 2009-09-17 for molding process for ridge vents and other index molded products.
This patent application is currently assigned to AIR VENT, INC.. Invention is credited to Phillip R. Grisham, Robert Bradley Holland.
Application Number | 20090233541 12/047064 |
Document ID | / |
Family ID | 41063558 |
Filed Date | 2009-09-17 |
United States Patent
Application |
20090233541 |
Kind Code |
A1 |
Holland; Robert Bradley ; et
al. |
September 17, 2009 |
MOLDING PROCESS FOR RIDGE VENTS AND OTHER INDEX MOLDED PRODUCTS
Abstract
A method of making a ridge vent includes: disposing a first
quantity of a polymeric material in a mold cavity; forming a first
ridge vent section in the mold cavity, the first ridge vent section
having a stepped end section formed across a width of the first
ridge vent section at an end thereof; indexing the first ridge vent
section so that it is substantially moved beyond the mold cavity
but remains in contact at the stepped end section with the mold;
disposing a second quantity of polymer between the mold sections;
and forming a second ridge vent section which is connected to the
first ridge vent section at the stepped end section. The stepped
end section includes bottom tread and top tread sections, wherein
the tread length of the bottom tread section has a non-uniform
tread length across the width of the bottom tread section.
Inventors: |
Holland; Robert Bradley;
(Rowlett, TX) ; Grisham; Phillip R.; (Dallas,
TX) |
Correspondence
Address: |
DUANE MORRIS LLP - Philadelphia;IP DEPARTMENT
30 SOUTH 17TH STREET
PHILADELPHIA
PA
19103-4196
US
|
Assignee: |
AIR VENT, INC.
Dallas
TX
|
Family ID: |
41063558 |
Appl. No.: |
12/047064 |
Filed: |
March 12, 2008 |
Current U.S.
Class: |
454/365 ;
264/255 |
Current CPC
Class: |
B29C 45/0003 20130101;
E04D 13/176 20130101 |
Class at
Publication: |
454/365 ;
264/255 |
International
Class: |
F24F 7/02 20060101
F24F007/02; B28B 7/18 20060101 B28B007/18 |
Claims
1. A method of making a ridge vent, comprising: providing a mold
having upper and lower mold sections forming a mold cavity
therebetween; disposing a first quantity of a polymeric material in
said mold cavity between said mold sections; forming a first ridge
vent section in said mold cavity, said first ridge vent section
having a stepped end section formed across a width of said first
ridge vent section at an end thereof; indexing said first ridge
vent section so that it is substantially moved beyond said mold
cavity but remains in contact at said stepped end section with said
mold; disposing a second quantity of polymer between said mold
sections; and forming a second ridge vent section which is
connected to said first ridge vent section at said stepped end
section, wherein said stepped end section comprises bottom tread
and top tread sections, wherein the tread length of said bottom
tread section has a non-uniform tread length across the width of
said bottom tread section.
2. The method of claim 1, wherein said first ridge vent section is
automatically indexed forward prior to forming said second ridge
vent section.
3. The method of claim 2, wherein said mold sections open and close
between forming said first ridge vent section and said second ridge
vent section.
4. The method of claim 1, wherein said disposing steps comprise
injection molding.
5. The method of claim 1, wherein said bottom tread section has a
plurality of spaced exhaust venting holes formed therethrough,
wherein said top tread section includes regions formed in between
at least some of said spaced exhaust venting holes.
6. The method of claim 1, wherein said non-uniform tread length has
a wave pattern.
7. The method of claim 1, wherein said non-uniform tread length has
a sawtooth pattern.
8. The method of claim 1, wherein said non-uniform tread length has
a rectangular serrated pattern.
9. A rollable ridge vent comprising a central panel having a
stepped end section formed across a width of said central panel at
an end thereof, wherein said stepped end section comprises a bottom
tread and top tread sections, wherein the tread length of said
bottom tread section has a non-uniform tread length across the
width of said bottom tread section.
10. The rollable ridge vent of claim 9, wherein said bottom tread
section has a plurality of spaced exhaust venting holes formed
therethrough, wherein said top tread section includes regions
formed in between at least some of said spaced exhaust venting
holes.
11. The rollable ridge vent of claim 10, wherein said non-uniform
tread length forms a wave pattern.
12. The rollable ridge vent of claim 10, wherein said non-uniform
tread length forms a sawtooth pattern.
13. The rollable ridge vent of claim 10, wherein said non-uniform
tread length forms a rectangular serrated pattern.
14. A method of making a ridge vent, comprising: providing a mold
having upper and lower mold sections forming a mold cavity
therebetween; disposing a first quantity of a polymeric material in
said mold cavity between said mold sections; forming a first ridge
vent section in said mold cavity, said first ridge vent section
having an end section formed across a width of said first ridge
vent section at an end thereof; indexing said first ridge vent
section so that it is substantially moved beyond said mold cavity
but remains in contact at said end section with said mold;
disposing a second quantity of polymer between said mold sections;
and forming a second ridge vent section which is connected to said
first ridge vent section at said end section, wherein said end
section comprises a recessed region comprising a plurality of
spaced exhaust venting holes formed therethrough and regions of
increased thickness formed between adjacent ones of said spaced
exhaust venting holes.
15. The method of claim 14, wherein said first ridge vent section
is automatically indexed forward prior to forming said second ridge
vent section.
16. The method of claim 15, wherein said mold sections open and
close between forming said first ridge vent section and said second
ridge vent section.
17. The method of claim 14, wherein said disposing steps comprise
injection molding.
18. The method of claim 14, wherein said end section comprises
bottom tread and top tread sections, said top tread section forming
said regions of increased thickness, wherein the tread length of
said bottom tread section has a non-uniform tread length across the
width of said bottom tread section.
19. The method of claim 14, wherein said regions of increased
thickness comprises islands within said recessed region.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to molding processes and more
particularly to index molding processes.
BACKGROUND OF THE INVENTION
[0002] Index injection and compression molding processes are
described in commonly assigned U.S. Pat. Nos. 6,881,144 and
6,991,535 to Ciepliski et al. (the "'144 and '535 Patents"), which
are both hereby incorporated by reference herein. More
specifically, these patents describe an index molding process for
use in forming rollable plastic ridge vents. As described in those
patents and illustrated in FIGS. 1 and 2 herein (reprinted from
FIGS. 9 and 10 of the '535 Patent), a mold 102 having upper and
lower mold sections, shown in phantom in FIG. 1, is provided for
forming a mold cavity. A quantity of polymeric material is disposed
in the mold cavity and a first ridge vent section 101, also shown
in phantom, is formed in the mold cavity. Next, the first ridge
vent section 101 is indexed so that it is substantially moved
beyond the mold cavity but remains in contact with the mold 102. As
shown in FIG. 2, a small stepped extension formed in the baffle and
central panel of the molded section 101, can remain in the mold
102. Finally, a second quantity of polymer is disposed between the
mold sections of mold 102 and a second ridge vent section is formed
which is connected to the first ridge vent section 101. The cooled
ridge vent sections can then be rolled up in a length containing
about 20 to 50 feet of vent material, which is then packaged in a
paper or polyethylene wrap.
[0003] The index molding method described above has proved to be an
efficient method of forming continuous lengths of rollable ridge
vent. But, the process is not without its problems. As described
above, the end of the indexed molded section 101 utilizes a stepped
extension across the width of the panel body which is overmolded
and forms a seamless connection between molded sections. The
present applicant has noticed that adjacent overmold-connected
sections can crack and separate in the area of this stepped section
in cold environments, such as during torqueing or unrolling of a
length of rolled ridge vent. While not wanting to be limited to any
one theory, the applicant believes that this cracking/separation is
the result of continuous stress concentration features that extend
laterally across the vent at the overmold location introduced, for
example, from rolling the ridge vent during packaging or bending of
the product during installation. Therefore, there is a need for an
improved molding process resulting in a more robust molded
product.
SUMMARY OF THE INVENTION
[0004] A method of making a ridge vent is provided including the
following steps: providing a mold having upper and lower mold
sections forming a mold cavity therebetween; disposing a first
quantity of a polymeric material in the mold cavity between the
mold sections; forming a first ridge vent section in the mold
cavity, the first ridge vent section having a stepped end section
formed across a width of the first ridge vent section at an end
thereof; indexing the first ridge vent section so that it is
substantially moved beyond the mold cavity but remains in contact
at the stepped end section with the mold; disposing a second
quantity of polymer between the mold sections; and forming a second
ridge vent section which is connected to the first ridge vent
section at the stepped end section. The stepped end section
includes bottom tread and top tread sections, wherein the tread
length of the bottom tread section has a non-uniform tread length
across the width of the bottom tread section.
[0005] In one embodiment, the end section comprises a recessed
region comprising a plurality of spaced exhaust venting holes
formed therethrough and regions of increased thickness formed
between adjacent ones of the spaced exhaust venting holes.
[0006] The above and other features of the present invention will
be better understood from the following detailed description of the
preferred embodiments of the invention that is provided in
connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The accompanying drawings illustrate preferred embodiments
of the invention, as well as other information pertinent to the
disclosure, in which:
[0008] FIGS. 1 and 2 illustrate a prior art index molding
process;
[0009] FIG. 3 is a partial perspective view of a molded section of
a rollable ridge vent for use in a prior art index molding
process;
[0010] FIG. 4 is a partial perspective view of a molded section of
a rollable ridge vent for use in the index molding process of the
present invention;
[0011] FIG. 5 is a flow chart illustrating the molding process of
the present invention;
[0012] FIG. 6 is an enlarged partial perspective view of an end
section of an alternative embodiment of the molded section of FIG.
4;
[0013] FIG. 7 is an enlarged partial perspective view of an end
section of another alternative embodiment of the molded section of
FIG. 4;
[0014] FIG. 8 is an enlarged partial perspective view of an end
section of another alternative embodiment of the molded section of
FIG. 4;
[0015] FIG. 9A is a top plan view illustrating an alternative
embodiment of the present invention and FIG. 9B is a enlarged
partial view of a portion of FIG. 9A; and
[0016] FIG. 9C is a top plan view illustrating another alternative
embodiment of the present invention.
DETAILED DESCRIPTION
[0017] This description of the exemplary embodiments is intended to
be read in connection with the accompanying drawings, which are to
be considered part of the entire written description. In the
description, relative terms such as "lower," "upper," "horizontal,"
"vertical," "above," "below," "up," "down," "top" and "bottom" as
well as derivative thereof (e.g., "horizontally," "downwardly,"
"upwardly," etc.) should be construed to refer to the orientation
as then described or as shown in the drawing under discussion.
These relative terms are for convenience of description and do not
require that the apparatus be constructed or operated in a
particular orientation. Terms concerning attachments, coupling and
the like, such as "connected" and "interconnected," refer to a
relationship wherein structures are secured or attached to one
another either directly or indirectly through intervening
structures, as well as both movable or rigid attachments or
relationships, unless expressly described otherwise.
[0018] As used herein, "index molding" is a process whereby a first
product is molded and then moved substantially outside of the mold.
A portion of the first molded product is left in contact with or
within the mold during molding of a second molded product, which is
molded to the portion of the first product left in contact with or
within the mold.
[0019] As described in the Background of the Invention section, the
end of the indexed molded section 101 has a stepped extension
formed across the width of the panel body. This stepped extension
remains in or is placed in the mold after the first section is
molded and is then overmolded upon formation of the next molded
section, forming a seamless connection between the two molded
sections and a continuous molded product. An example of this
stepped section (identified by reference number 200) is shown in
the partial perspective view of FIG. 3, which shows a molded ridge
vent section similar to that shown in FIG. 1 of commonly assigned
U.S. patent application Ser. No. 11/238,315 (hereinafter, the "'315
Patent Application"), published as U.S. Patent Publication No.
2007/0072540, the entirety of which is hereby incorporated by
reference herein. Applicant has learned that ridge vents formed
using the index injection molding process described above are prone
to cracking or separation in the area of the stepped section 200,
particularly in cold temperatures. The previous design includes
continuous geometric stress concentration features at the overmold
seam that make the product substantially weaker at these locations
compared to other locations down the length of the vent. In this
design, cracking propagates from the stepped seam feature at the
overmold section. Fracturing has been observed at the step near the
riser wall on the top surface and at the very end of the vent
(furthest outboard section of the tread) on the underside of the
vent, depending on the direction of the bending moment applied to
the vent.
[0020] An exemplary process for forming a rollable ridge vent, such
as that described in the '144 and '535 Patents or in the '315
Patent Application is described hereafter in connection with FIGS.
4-7. Turning first to FIG. 4, FIG. 4 is a partial perspective view
of a molded section of a rollable ridge vent for use in the index
molding process described above in connection with FIGS. 1 and 2
and hereafter. The ridge vent section is identical in all respect
to the ridge vent section shown in FIG. 3 and described in the '315
Patent Application except for the configuration of the stepped end
section 200A at the end of the ridge vent section. It should be
understood that FIG. 4 illustrates an intermediate product (like
molded section 101 of FIGS. 1 and 2) that is used in forming a
longer length of rollable ridge vent. With reference to terms
commonly used to identify step components, the stepped end section
200A includes a bottom tread section 202, a riser wall 204 and a
top tread section 206. The top tread section 206, which is
essentially the top surface of the central panel portion 208 of the
ridge vent section, is connected to the bottom tread section 202 by
the riser wall 204. The bottom tread section 202 can also be viewed
as a recess in the central panel 208 or a region of less thickness
when compared to top tread section 206.
[0021] Returning to FIG. 3, it can seen that the tread length (also
known as "tread depth"), defined as the distance between the edge
of the tread and the riser wall, of the bottom tread section is
uniform across the width of the central panel of the ridge vent. In
contrast, with respect to the embodiment of FIG. 4, the tread
length is non-uniform across the width of the central panel 208 and
tread section 202. Specifically, the tread length of the bottom
tread section 202 varies in a wave pattern. In the illustrated
embodiment, the wave pattern locally interposes the top tread
section 206 in between adjacent exhaust venting holes 210 (which
may be a contributing factor to the cracking noted above with the
prior design) used during the molding process in the illustrated
embodiment, though this specific location with respect to the
venting holes is not a requirement of the invention. In this
manner, the top tread section 206 forms a joint or seam with a
second ridge vent that is interrupted (i.e., not straight) when a
second ridge vent section overmolds the bottom tread section 202 of
the ridge vent section of FIG. 4. It is believed that the portions
of the second tread section 206 that are interposed between the
spaced exhaust venting holes 210 provide undulating or interrupting
features that eliminate the continuous, linear stress concentration
feature of the previous design shown in FIG. 3. These undulating or
interrupting features operated to deter or stop the propagation of
cracks formed at the overmold location.
[0022] An exemplary molding process using the ridge vent section of
FIG. 4 is described in connection with the flow chart of FIG. 5.
The preferred index molding process of the present invention is an
injection molding process, though the index process may be used
with compression, extrusion or other molding processes. At step S1,
a selected polymer material is disposed in a mold cavity of a mold.
As will be understood from FIGS. 1 and 2 and the description of the
'144 and '535 Patents, the mold includes upper and lower mold
sections that define a mold cavity therebetween. The mold cavity
defines the shape (in negative form) of the mold section shown in
FIG. 4, including its end section 200A.
[0023] At step S2, a first molded ridge vent section (such as shown
in FIG. 4) is formed in the mold. As those familiar with the art of
molding will understand, molded products are formed in molds by
controlling process parameters such as injection speed, material,
mold temperature and pressure.
[0024] At step S3, the mold sections are opened and the so-formed
first molded ridge vent section is ejected or indexed, leaving the
end shown in FIG. 4 in contact with the mold. More specifically,
the stepped section 200A is left in contact with the mold so that
the bottom tread 202 can be overmolded during the formation of the
next molded section in the mold. This step, as well as others, is
preferably automated.
[0025] At step S4, the mold sections are closed and a second amount
of polymer is disposed in the mold cavity to form a second molded
ridge vent section, in the manner described above in connection
with steps S1 and S2. This second ridge vent section has an end
that is overmolded with the stepped section 200A of the first mold
section, forming a continuous length of ridge vent.
[0026] If the desired number of molded sections have been formed
and molded together (step S5), then the process ends at step S6,
i.e., the mold is opened and the product is removed for later
processing (e.g., rolling and packaging). If one or more additional
sections are required, then the process returns to step S3 to index
the second molded section so that a third molded section can be
formed and connected to the stepped end of the second molded
section. Of course, the product can be run continuously and cut to
length outside of the mold (downstream of the overmolding process)
while manufacturing continues.
[0027] A rollable ridge vent was formed using the process of FIG. 5
and using the stepped end section design having a non-uniform tread
length shown in FIG. 4. This rollable ridge vent was tested. The
tests revealed excellent results even at temperatures as low as
negative 20.degree. C. Overmolded samples of the ridge vent product
were conditioned to temperatures below freezing for a period of at
least 24 hours. The samples were then subjected to bending and
reverse bending loads. Stress marks and crack propagation were
noted for samples of the designs illustrated in FIGS. 3 and 4. The
design incorporating the undulating or sinusoidal tread feature of
FIG. 4 performed substantially better than the tread feature of
FIG. 3. Cracking did not propagate along the length of the overmold
seam for this new design.
[0028] Although a wave or sinusoidal edge pattern for the treads is
shown in FIG. 4, other patterns may be used that result in a
non-uniform tread depth. For example, FIG. 6 shows an enlarged
partial perspective view of an end section of an alternative
embodiment of the molded rollable ridge vent section of FIG. 4.
FIG. 6 shows an end section where the step section 200B has a
sawtooth shape formed from bottom tread section 202B and top tread
section 206B. The top tread section 206B extends towards the edge
of the ridge vent section to separate the spaced exhaust venting
holes 210.
[0029] By way of another example, FIG. 7 shows an enlarged partial
perspective view of an end section of another alternative
embodiment of the molded rollable ridge vent section of FIG. 4.
FIG. 7 shows an end section where the step section 200C has a
rectangular serrated shape formed from bottom tread section 202C
and top tread section 206C. In this embodiment, the tread
length/depth of the bottom tread section 202C is non-uniform in so
much as it has zero or no length at, for example, points A and a
different length at, for example, points B. The top tread section
206B extends towards the edge of the ridge vent section to separate
the spaced exhaust venting holes 210.
[0030] Although FIGS. 4, 6 and 7 show tread patterns having
periodic shapes, this is not a requirement. Non regular patterns
can be selected as long as some interference is presented along the
length of the overmold seam. Further, an alternative way to view
the stepped end section is not by way of tread length, but rather
by way of thickness of the panel section 208. In embodiments, the
panel 208 is designed such at least some areas, such as areas
formed between exhaust venting holes, are thicker than the areas
that are recessed for being overmolded during the formation of a
second molded section. For example, as shown in FIG. 8, the end
section 200D can include interference islands 206D formed between
exhaust venting holes within bottom tread section 202D. This
embodiment can increase the amount of recessed area in the end
section that can receive polymer during the formation of the second
molded section, thereby improving the overmold connection between
two sections. Further, in the embodiments shown in FIGS. 4, 6 and
7, the top tread sections 206, 206B and 206C need not extend all
the way to the end edge of the ridge section.
[0031] The panel disclosed herein is preferably formed from
relatively high impact (non-brittle) polymer materials, such as, by
way of example only, polypropylene or polyethylene.
[0032] FIG. 9A is a top plan view of an alternative embodiment of a
rollable ridge vent with the molded seam joining two sections A and
B shown in dashed line. FIG. 9B is an enlarged partial view showing
only a portion A' of section A. The seam is shown in dashed form
because the vent sections are already molded together as described
above in connection with FIG. 5. That is, section A is first formed
in the manner shown in FIG. 5 and then indexed, after which the
mold cavity is again filled with polymer to form a second section B
that is molded to (not necessarily overmolded on) the end of the
first section A. FIG. 9B is an enlarged portion A' of vent section
A from FIG. 9A illustrating a portion of the end of section A prior
to being molded to subsequently formed section B. As shown in both
FIGS. 9A and 9B, the end of section A need not have a ledge that is
overmolded by the polymer in forming the second section B. In this
embodiment, the edge takes a non-straight (zig-zag or notched)
shape, such as a dovetail shape comprising teeth 300. The edge is
made discontinuous in the X-direction across the width of the vent
section. Alternatively, or in addition thereto, the distance in the
Y-direction of the edge from a given reference line perpendicular
to the Y-direction (e.g., the X-axis) varies, such as in the
sinusoidal manner best illustrated in FIG. 9A. As with the
embodiments of FIGS. 4 and 6-8, the discontinuities of the edge
shape help to prevent the propagation of cracks and fractures along
the mold seam similar to the embodiments described above in
connection with FIGS. 4, 6, 7 and 8. Put another way, the notched
edge prevents the formation of a continuous straight seam between
sections A and B that is prone to crack and fracture
propagation.
[0033] Another embodiment is shown in FIG. 9C. This embodiment is
similar to the embodiment shown in FIG. 9A only additional
discontinuities are provided in the teeth 300' of the edge of
section A in the form of lateral steps 302 formed in the
Y-direction.
[0034] Although the invention has been described in terms of
exemplary embodiments, it is not limited thereto. For example,
although the improved configurations are described for use with
forming lengths of rollable ridge vent, these configurations could
also be used in the formation of other index molded products where
it is desired to improve the bond between sections molded together.
The appended claims should be construed broadly to include other
variants and embodiments of the invention that may be made by those
skilled in the art without departing from the scope and range of
equivalents of the invention.
* * * * *